At present, mobile communication technology is applied widely in daily life. However, encryption is not performed in most processes of communication, and hence a third party is easy to intercept the communication. Although some operators encrypt a data flow in the stage of wireless transmission process, it is required that the data flow is in an encrypted state during the whole transmission processes in the case of a higher secret requirement, to avoid being intercepted in some middle stages of the transmission. Therefore, end-to-end encryption needs to be applied in a mobile communication process. That is, encryption and decryption are performed by a calling terminal and a called terminal, respectively. In this way, user information security can be protected effectively, no matter which network the data flows through.
In general, a mobile terminal does not have a function of supporting end-to-end secret communication. In some existing technologies, hardware of the mobile terminal is usually reconstructed firstly by adding an encryption-decryption module, a key storage module and the like, to form a special mobile terminal which supports a certain secret communication way. However, the above solution has the following disadvantages. In the first aspect, the cost is high. A new type of terminal needs to be designed and produced only for a secret communication function, which is not conductive to popularizing the new designed terminal due to a high technical requirement. In the second aspect, from a user perspective, most of users want their current mobile terminal to have the secret communication function, instead of replacing their current mobile terminal with a new mobile terminal only for the secret communication function.
As the popularization of an Android intelligent operating system in recent years, a market share thereof is increasing. It is possible to add secret communication function with high security to an Android intelligent cell phone or other Android intelligent mobile terminal in a pure software way while maintaining original functions thereof. At present, there are some simple communication encryption tools under an Android environment or other mobile operating system in the market, for example, small application software such as short message encryption. However, since keys are difficult to be distributed, the encryption is performed with a mathematical algorithm or by reusing (or reusing in variations) the key. Alternatively, one or more file/key blocks in a permanent storage medium of the mobile terminal are directly used as service keys for each call. However, the keys are easy to be broken or be broken after being exported, which can not be applied to a scenario having a high security requirement. Moreover, at present, the encryption communication software with such security intensity is generally limited to encrypt small amount of information such as a short message on an intelligent mobile platform, and can only protect specified one or more services. It is very short of a universal secret intelligent mobile terminal platform capable of providing a one-time pad for a large data amount communication service such as a VoIP call and a video call. A method for encrypting information with application software is still unreliable. It is because that the software is installed in Android operating system; and if the software can be installed by the user, it can also be maliciously uninstalled by an attacker. Therefore, the software has poor security and is not adapted to the scenario having a high security requirement.